The Air Force has been secretly flying armed Reaper drones on counterterrorism missions from a remote civilian airport in southern Ethi­o­pia as part of a rapidly expanding U.S.-led proxy war against an al-Qaeda affiliate in East Africa, U.S. military officials said.

The Air Force has invested millions of dollars to upgrade an airfield in Arba Minch, Ethi­o­pia, where it has built a small annex to house a fleet of drones that can be equipped with Hellfire missiles and satellite-guided bombs. The Reapers began flying missions earlier this year over neighboring Somalia, where the United States and its allies in the region have been targeting al-Shabab, a militant Islamist group connected to al-Qaeda.